Do a search on focused ultrasound (FUS), and you'll quickly discover that it's a kind of fairy-tale cure, helpful in the treatment of almost everything: Parkinson's disease, uterine fibroids, atrial fibrillation, congestive heart failure, Alzheimer's disease, depression, diabetes, obesity, cancers of the prostate, kidneys, pancreas, bladder, breast, and dozens more.
FUS also has its own website, run by the Focused Ultrasound Foundation, a manufacturer-supported organization dedicated to "accelerating the development and adoption of focused ultrasound." Neal Kassell, MD, the founder and chairman of the foundation and a professor emeritus of neurosurgery at the University of Virginia School of Medicine, said in a that FUS "could improve the health and happiness of millions of people around the world."
The technology has not, however, been greeted with universal acclaim. It has proven controversial enough in the treatment of essential tremor -- for which it has FDA approval -- that the American Academy of Neurology's 2017 meeting this week featured it in a plenary-session "controversies in neurology" debate.
At that session, Paul Fishman, a neurologist at the University of Maryland, took the "pro" side, arguing that serious adverse event rates with FUS are dramatically lower than with a more established alternative -- deep brain stimulation (DBS). Fishman also said that DBS has a significant incidence of hardware failure requiring additional surgery.
Michael S. Okun, MD, the chairman of neurology at the University of Florida -- who argued the "con" side -- did not dispute those points, but noted that the opportunity for later surgery was an advantage, because mistakes and complications can often be corrected. That's not possible with FUS, which burns away tissue. "You can't troubleshoot a focused ultrasound problem," he said.
Okun also noted that the target for FUS in Parkinson's disease is very small -- "the size of a squashed pea" -- and can't be visualized well in MRI scans. That, along with difficulties focusing the beam because of interference from the skull, means off-target ablation is likely to occur periodically. And FUS can be used on only one side of the brain, because thalamic ablation on both sides has consistently been shown to have unacceptable adverse effects. DBS, in contrast, can be safely used on both sides to achieve more complete symptom control.
Okun did acknowledge that FUS holds a great deal of promise for other neurological applications, calling the potential of using it to open the blood-brain barrier to allow larger molecules into the brain, "brilliant."
In an interview the day before the debate, Okun said that using FUS to treat essential tremor "is like trying to make an omelet without opening the egg ... You're shooting from outside the brain." And the targets are not only small but also "somatotropically organized." Particular regions of the brain are mapped to specific parts of the body, and a misplaced lesion can have harmful side effects. A wrongly mapped attempt to ease a tremor in an arm, for example, could weaken a leg, leaving a patient unable to walk, Okun said.
Further, he said, neurologists already have a powerful means of treating essential tremor. "The gold standard of making lesions in the brain is radiofrequency [ablation]. Once you've mapped a brain out and you know where the structures are, you can insert a probe and burn it."
Fishman said before the debate that the use of FUS for Parkinson's disease could be a cheaper alternative to deep-brain stimulation. And he said he is eager to see it approved by the FDA, because until then it isn't covered by insurance. "We have a waiting list of over 200 patients," he said, but he can do the procedure only on those who can pay $25,000-$35,000 out of pocket. Asked if he was excited about FUS, he said, "It's a gas!"
At the conclusion of the AAN debate, audience members were asked whether they sided with Okun or Fishman. Okun's arguments "con" won with 90% of those voting, but most audience members didn't raise their hands for either one, suggesting that they found both sides persuasive.
Kassell acknowledged the criticism, but it doesn't dampen his enthusiasm. He was able to persuade a Charlottesville, Va., neighbor, John Grisham, the best-selling author of legal thrillers, to write a short book called The Tumor, which shows how FUS could one day be used to treat glioblastoma. "This is not fiction," Grisham said. "This is the future, and it is rapidly approaching."
FUS operates by a variety of mechanisms, including ablating tissue, delivering drugs in high concentrations to a particular point in the body, and enhancing the effectiveness of cancer immunotherapy drugs -- 18 different mechanisms in all.
Kassell said there are several areas in which the technology is nearest to routine use. One is to deliver drugs to a precise target. The drugs can be tucked inside hollow lipid spheres which are injected into the bloodstream. "You can inject millions of these into the bloodstream, and they are everywhere blood goes. But the drug is inactive except where the ultrasound is focused. At that point the microbubble bursts and delivers its pharmacological payload," Kassell said.
A second is to ablate tissue, and a third is to modulate the immune system, meaning ultrasound might have a role to play in enhancing the effectiveness of cancer chemotherapy or other drugs.
Kassell said FUS has been approved by the FDA for three things in addition to essential tremor: uterine fibroids; pain from bone metastases; and the ablation of prostate tissue to treat prostate cancer or BPH. But more are coming.
"As of today, there are almost 80 clinical indications in various stages of research and development," Kassell said. He notes that FUS can potentially be much cheaper than alternative treatments. Deep-brain stimulation for Parkinson's disease costs some $60,000 to $100,000, he said, but ultrasound can do the job for one-third of that. (Okun said in the interview that data does not yet exist to show that FUS is cheaper.)
Kassell said that the foundation works with three dozen companies that make ultrasound equipment, but that the foundation is not intended to promote commercial interests -- only to spread interest in what he sees as an extremely valuable new technology. "What we're doing here at the foundation is to be engaged in a variety of activities which can move quickly to save people and save lives," he said.
Prostate cancer is one of the applications for which ultrasound looks most promising. Last year, at the annual meeting of the American Urological Association, researchers reported that almost 90% of patients with early prostate cancer remained free of radical intervention two years after treatment of a single lobe with high-intensity FUS. The report generated "cautious optimism" that the technology could play a role in the treatment of early prostate cancer.
Another application is for use with Alzheimer's disease. FUS's ability to gently open the blood-brain barrier can allow amyloid-scavenging drugs to reach and potentially destroy plaques characteristic of Alzheimer's disease.
The first human trials for Alzheimer's disease were launched in March by a neurosurgeon, Nir Lipsman, MD, PhD, at Sunnybrook Health Sciences Center in Toronto. Two of a total of six patients were treated to assess the safety of the technique before it's used more widely.
Other Alzheimer's specialists were divided over whether or not human trials are premature, but because ultrasound has been used in the brains of Parkinson's patients, some felt that it was likely to be safe for use in Alzheimer's disease. The study is also predicated on the fact that the plaques are a cause of the illness; not everyone agrees that that's the case.
Now we come to the question: Is FUS a wise buy?
"I would say definitely yes," said Fishman. "There is a product out there already, which is deep brain stimulation. For a certain fraction of those patients, they would likely opt for FUS, which is a cheaper technology, and less onerous." Asked if neurologists are excited by FUS, Fishman said, "The field is still very unaware of this technology. There may be a thousand articles in the medical literature on DBS and maybe 50 on this." He also offered "a little disclaimer ... I have the passion of a recent convert."
Asked the same question, Kassell said, "The answer is ... it depends." The economics will be hard to sort out until insurance companies begin to cover it, he said. "Some sites can fight with the insurance companies, but there is not a lot of reimbursement. People are paying cash."
At the same time, he's frustrated and unhappy at the pace of research. Asked if he was enjoying this work during what could be a relaxing retirement, he said no. Too often, he said, he sees people who could be helped, and he knows that the data is not yet there to offer them the treatment.
Kassell's vigorous promotion of FUS could backfire -- it invites skepticism. Far too many treatments that work like magic in mice or a handful of patients fail in proper clinical trials.
It's too soon to know whether FUS is one of them. It's not yet a wise buy. But when the evidence comes in, it might be. It's simply too early to dismiss it or embrace it.
Wise Buy, a 乌鸦传媒 series, assesses therapies -- new and old -- to determine if the treatment is not only a wise choice, but also a wise buy.